Use of the Earth's resources has resulted in global scale environmental problems including elevated atmospheric carbon dioxide (CO2) concentrations and significant depletion of living marine resources. As a result of land use change and the burning of fossil fuels, atmospheric CO2 levels are predicted to double in as little as 60 years. It is expected that elevated atmospheric concentrations of CO2 and other greenhouse gases will facilitate greater storage of heat within the atmosphere leading to enhanced surface temperatures and rapid climate change. The impact of climate change will likely be economically expensive and environmentally hazardous. Reducing potential risks of climate change will require sequestration of atmospheric CO2.
Methods proposed to capture and store atmospheric CO2 include storage in geological formations, injection into the deep ocean, and uptake by phytoplankton via fertilization of the ocean. The limited capacity and duration, expense, and environmental outcomes of these methods are largely unresolved and may prohibit their utility.
The most economically and environmentally plausible manner to sequester atmospheric CO2 is to enhance natural sinks. Natural options avoid the costs associated with industrial separation, capture, compression, and storage of carbon dioxide, and reduce potential negative environmental side effects. Natural methods offer reservoirs of large capacity and the ability to replace the carbon from whence it came, the long-term carbon cycle. Enhancing forest growth is an example of a natural method of carbon sequestration that is environmentally benign and, with proper management, allows for the value-added option of sustainable forestry harvest. The largest natural carbon reservoirs include ocean waters and marine sediments.
The flux of organic matter from surface waters to the deep ocean has a direct influence on the partitioning of CO2 between the ocean and the atmosphere. In general, the greater depth that particulate organic carbon (POC) sinks to before remineralization, the longer time it takes to return to surface waters as dissolved carbon where it may reenter the atmospheric carbon cycle. Carbon that reaches the intermediate and deep ocean is entrained in water masses that have longer flow pathways back to the surface and smaller advective water velocities than in the upper ocean. The thermohaline ventilation of ocean interior waters occurs on time scales ranging from between annual and hundreds years in the upper ocean (approximately <2 km) to up to a 1000 years in the deep ocean (approximately >2 km). Buried carbon entering the geological record will be isolated from the atmosphere for millions of years. Thus, an effective method of carbon dioxide sequestration would be to promote the flux of organic matter from surface waters to the deep ocean. Accordingly, there is a need in the art to develop methods of promoting this flux for the purposes of carbon dioxide sequestration.